Dumb CEL question... regarding HPOP pressure - Diesel Forum

ryanPSD · 01-30-2006, 03:52 AM

Whenever I feel like causing a ruckus (chip turned up, 5th gear, 800rpm WOT) [img]/ubbthreads/images/graemlins/smokin.gif[/img] [img]/ubbthreads/images/graemlins/smokin.gif[/img] [img]/ubbthreads/images/graemlins/smokin.gif[/img] and getting a CEL from the low HPOP pressures... as soon as I am able, I shut off the engine and restart to clear the light.

But my question is, am I fine just continuing on driving without doing that? Or does anything go into a "limp" mode or get reset to a certain value (like when you unplug the ICP it defaults to like 500 I think?) until the engine is restarted?

CraigPSD · 01-30-2006, 09:11 AM

As I understand it, the truck defuels itself and your fuel milage goes way downhill. I have had no ill effects from driving several miles with a CEL from low oil pressure.

Craig

Hpop · 01-30-2006, 09:36 AM

No issues with "hurting" the engine by driving with a CEL or SES from low high pressure oil.

gtspowerstroke · 01-30-2006, 09:44 AM

Yes it goes into a "limp home mode" and defuels until you restart.

TimMiller · 01-30-2006, 11:39 AM

What does it do when it goes into a limp mode? I never noticed any difference when i set a CEL.

Hpop · 01-30-2006, 12:49 PM

I can't comment on a "CEL" so much, but when I used to set an SES light, the truck was noticably falling on it's face after that until I cleared the light. Just seems to pull back the fuel on top.

.02

ryanPSD · 01-30-2006, 02:39 PM

I've noticed no difference after the light came on. [img]/ubbthreads/images/graemlins/shrug.gif[/img]

One example is in my little video a while back where I bolted my camera underneath the frame, after a big [img]/ubbthreads/images/graemlins/smokin.gif[/img] [img]/ubbthreads/images/graemlins/smokin.gif[/img] [img]/ubbthreads/images/graemlins/smokin.gif[/img] I had a CEL and still took off really hard afterwards...

ThreeStarJR · 01-30-2006, 06:48 PM

Ryan, Bean said that throwing that cel had no effect on performance, just that it's a dang nuisance for it to run out of oil and lay down, and then be staring @ a cel until you restart.....

swh22 · 01-30-2006, 09:05 PM

I can definitely feel a difference on mine after a cel, it's like setting it back into stock mode. Does it have to do with the ECM codes maybe? I also noticed a power drop with the over-boost and fixed it with a regulator. Maybe this is something that only started up in 97?

ryanPSD · 01-31-2006, 12:02 AM

[ QUOTE ]
Ryan, Bean said that throwing that cel had no effect on performance, just that it's a dang nuisance for it to run out of oil and lay down, and then be staring @ a cel until you restart.....

[/ QUOTE ]

That's what I was thinking. The light is just annoying to look at. [img]/ubbthreads/images/graemlins/frown.gif[/img]

[ QUOTE ]
I can definitely feel a difference on mine after a cel, it's like setting it back into stock mode. Does it have to do with the ECM codes maybe? I also noticed a power drop with the over-boost and fixed it with a regulator. Maybe this is something that only started up in 97?

[/ QUOTE ]

I'd doubt it's a PCM thing, I am running TDE1, isn't that the latest (aka 97)?

GSXRTURBOQUAD · 01-31-2006, 12:59 AM

What is your HPOP pressure at WOT? Mine did the same. Only dropped 500lbs. You need Big Oil! [img]/ubbthreads/images/graemlins/wink.gif[/img]

ryanPSD · 01-31-2006, 02:16 AM

Big oil? *NOOOOOOOOOOOOOOOOO*

I think I just heard my checking account scream [img]/ubbthreads/images/graemlins/shrug.gif[/img] Anyone else hear that?

Don't think I can do big anything (turbo, oil, etc), except maybe fuel someday... I need to slow down.

Anyway, I have no idea. I have no scanner or gauge. I know it falls on its face as the CEL is set (obviously), but my main question is about oil pressure/performance/whatever after the light is set. [img]/ubbthreads/images/graemlins/shrug.gif[/img]

Vengeance · 01-31-2006, 07:28 AM

On the OBS trucks, when you throw the CEL for low ICP, then the truck will limit fuel deliver until it sees the hpop come back into its normal duty cycle for a few seconds, then it will go back to normal. The CEL stays on though until you cycle the key. On the superduty's they SES light will come on and it will limit the fuel until it comes back into parameters, then it will clear the light and business as normal. The OBS trucks do have conditions where it will go into a default mode and see fixed parameters until the key is cycled or the problem is fixed. If you throw the CEL due to tranny issues, the pcm will jack the line pressure and you'll have hard shifts depending on the reason for the CEL. If your MAP sensor goes out and it defaults, CEL comes on, tranny pressures increase, because line pressure is based on part from the MAP input, and you'll have firmer/harsher shifts until you fix the MAP. Not all things that cause a CEL will limit fuel to the truck.

TimMiller · 01-31-2006, 12:07 PM

[ QUOTE ]
If your MAP sensor goes out and it defaults, CEL comes on, tranny pressures increase, because line pressure is based on part from the MAP input, and you'll have firmer/harsher shifts until you fix the MAP. Not all things that cause a CEL will limit fuel to the truck.

[/ QUOTE ] Tranny pressure isn't based off of map. Unplug MAP CEL comes on and pcm will run off of default values which is like 16 if i remember correctly. If you unplug your ICP sensor the tranny will go into limp mode. B/c of the tranny line pressure working with the HP Oil pressure or something like that.

Hpop · 01-31-2006, 12:32 PM

I don't know Tim, I would think the tranny would surely look to the engine's main source for "load" data, being the map sensor. I believe the tranny uses the EOT sensor not the ICP sensor, but don't blame me if that's totally wrong, lol, I drive a manual. But I believe the EOT modifier table has connections with the tranny, especially in the light of some people (dangerously) playing games with the EOT sensor just as with the ICP sensor trickery, seeing strange reactions in auto trannies after tricking the EOT sensor into thinking it's colder out, obviously having affects on the injection timing and ICP among other variables.

If the tranny doesn't use the map sensor for load input, I would find that strange. But if the default values in your PCM are close enough to those in the environment or at least a good median of them, your other functions would still go on without much notice in variation after you unplugged the sensor in question.

.02

Take Care~